Service manual

CIRCUIT DESCRIPTION
6-17
Month 2000
Part No. 001-2004-601
Pin 13 TX MOD
The audio from the MAC in the Controller pro-
cesses a number of inputs to the station per the TIA
specifications to produce the signal on this pin. This
signal goes through the RFIB to the Exciter. A 707
mV RMS (2V P-P) sine wave at 1 kHz provides 60%
of system deviation in the transmitter. The DC volt
-
age on the line is 3.5V ±0.1V. The source impedance
should be low (output of an op-amp or analog switch
< 200 ohms) and the input impedance will not be less
than 10k ohms.
Pins 14-15 GROUND
These pins carry ground current between the
RFIB and the Exciter board.
Pin 16 SYN LK EX
Pin 16 is the Exciter synthesizer lock detector
output. The synthesizer is locked with a TTL logic
high state.
Pin 17 HS LK EX
Pin 17 is not used at this time.
Pin 18 HS CS EX
This input is not used at this time.
Pin 19 RF CLK
The clock controls the Exciter synthesizer when
loading. The input source in the Controller is TTL
with the speed determined by the synthesizer chip.
There could be as many as four synthesizers and a
shift register.
Pin 20 RF DATA
Pin 20 is a data pin from the Controller which has
the dual role of loading the synthesizer chip and
adjusting the power control D/A lines for proper out
-
put power. The data has TTL levels. Up to four syn-
thesizer chips and a shift register could be connected
to this pin.
6.4.6 RECEIVER CONNECTOR (J103)
The connector from the Receiver (J201) to the
RF Interface board (J103) links the Receiver to the
MPC in the Controller Backplane.
Pin 1 VCC1
Pin 1 is fused +15V ±1% with a nominal current
of 1A provides current from the RFIB to the Receiver.
Pins 2-6 UNUSED
Pin 7 RSSI
This pin is the Receive Signal Strength Indicator
(RSSI) to the Controller. The RSSI is used for tune-
up of the Receiver front-end during test mode. The
dynamic range is 60 dB. Output is from an op-amp
with the voltage going from 0.5V to 4.5V. The level
has an adjustment in the Receiver (see Section
6.1.4 or
6.1.5).
Pin 8 UNUSED
Pin 9 RX WBAND
The receive wide band audio is from the demodu-
lator and goes to the Main Audio Card (MAC) in the
Controller card cage. The typical amplitude is 387
mV RMS (-6 dBm) and 2V DC with Standard TIA
Test Modulation into the Receiver. Little wave shap
-
ing is done on the Receiver board other than a 31 kHz
RC LPF which strips off the 450 kHz IF. Buffering is
done with an op-amp which can drive a 10k ohm load.
Pin 10 UNUSED
Pin 11 GROUND
Pin 11 carries ground current between the RFIB
and the Receiver board.
Pin 12 SYN CS RX
Pin 12 is the Receiver synthesizer chip select.
This chip is the same part as used in the Exciter. A
low enables loading the Synthesizer.